The use of film cartridges in the x-raying of human teeth is well known. Such film cartridges are placed on one side of the teeth to be x-rayed and the teeth are then irradiated by the x-ray machine from the opposite side.
Periapical radiographs provide the dentist with a complete x-ray of a tooth from the crown to the root. Therefore, a film cartridge used in a periapical radiograph must be large enough to cover the entire tooth and must be placed such that the entire tooth is x-rayed. In order to obtain a minimum of distortion in the exposure, a technique known as "paralleling" is used. This technique involves placing the film cartridge in a plane substantially parallel to the long axis of the tooth to be x-rayed. The film cartridge must remain in this plane during the x-raying process to obtain a proper exposure.
Often a bite-wing film cartridge is used wherein a tab folds out in a substantially perpendicular direction from the film cartridge. The tab is bitten down upon by the patient in order to hold the film cartridge in place during the x-ray process and thus insure a proper exposure. Bite-wing x-rays are typically used for detecting interproximal cavities. Bite-wing x-rays do not require exposure of the root tips as with periapical exposures.
The requirements for size and precise placement of the film cartridge cause significant problems for the patient. It is difficult to place the film cartridge in an optimal position and to maintain that position. The edges of the film cartridge commonly abrade the gums and soft tissues of the mouth, causing significant discomfort and occasionally even intense pain. This problem is particularly significant with children due to their lower tolerance of pain. Children are more likely to change the position of the film cartridge within their mouth to alleviate discomfort. This action causes deterioration in the quality of the exposure. Often the patient is required to cooperate in maintaining the placement of the film cartridge by biting firmly on the bite-wing tab. It can be extremely difficult to obtain this cooperation when such an optimal placement of the film cartridge results in severe discomfort to the patient.
There are two types of film cartridges in common use. The first type utilizes a stiff paperboard covering. The edges of the paperboard covering are hard and can cause considerable pain when abrading the gum and soft tissues of the mouth. The second type of film cartridge has a plastic covering which is heat sealed about its perimeter. The plastic cartridge has a thinner and more flexible edge. However, the edge of the plastic cartridge is somewhat sharper than that of the paper cartridge. The plastic cartridge, therefore, also causes considerable pain and discomfort when used.
Cushions for radiographic dental film are disclosed in prior art U.S. Pat. No. 1,994,579, issued to Hodgson, U.S. Pat. No. 1,537,925, issued to Bolin, U.S. Pat. No. 1,631,497, issued to Marler, and U.S. Pat. Nos. 4,626,216 and 4,805,201, both issued to Strong-Grainger. The Hodgson patent discloses a dental film cartridge that has an absorbent pad structure attached to one surface of the film cartridge. The absorbent pad structure extends across the surface of the dental film cartridge, thus completely covering one side of the cartridge. While the Hodgson dental film cartridge does alleviate the problem of discomfort, it does so by increasing the bulk of the film cartridge. It not only significantly increases the cost of the film cartridge, but also makes it considerably more difficult to obtain properly exposed radiographs.
It should be noted that the "bisecting" method of obtaining radiographs was popular at the time the Hodgson device was invented. The "bisecting" technique permitted the placement of the film cartridge at a more comfortable angular orientation within the patient's mouth. The presently used "paralleling" technique requires much more precise positioning of the film cartridge.
The absorbent pad of the Hodgson device increases the thickness of the film cartridge considerably. It also increases the overall cartridge dimensions by a considerable amount, thereby making the film cartridge significantly taller and wider. Such increased size renders the Hodgson device more difficult to position properly, and therefore undesirable for use in the "paralleling" technique. The pad of the Hodgson device is constructed of pressed absorbent cotton. While this generally increase comfort to the patient, it will not compress significantly when pressed against the soft tissues of the sublingual mucosa below the patient's tongue or the hard or soft pallet above the tongue.
The Bolin patent discloses a dental film cartridge having a thick bead about the perimeter. The bead is intended to decrease the amount of discomfort experienced by the patient. The bead is formed of an elastomer which extends about the periphery of the film cartridge. This device, like the Hodgson device, increases the overall length and width substantially, thereby making placement in the "paralleling" method significantly more difficult.
The Marler patent discloses a dental x-ray film cartridge having a thin flexible bead about its periphery which alleviates to some extent the positioning problems caused by the increase in cartridge size associated with the Hodgson and Bolin devices. The Marler device utilizes a peripheral bead similar in structure to a rubber band and does not significantly increase the length, width or thickness of the film cartridge. The Marler device does not cover one entire surface of the cartridge as do both the Hodgson and Bolin devices. The primary problems associated with the Marler device are a comparatively high cost of manufacture and difficulty of use.
The Marler device is formed by the injection molding process. It thus requires comparatively expensive tooling and has a comparatively high per unit manufacturing cost. Installation of the Marler device upon a film cartridge is relatively difficult since the Marler device necessarily has a smaller inside perimeter than the perimeter of the film cartridge. This is required since the Marler device relies upon the elastic characteristic of the rubber material from which it is constructed to secure it about the periphery of the film cartridge. Thus, the user is required to stretch the Marler device sufficiently that the film cartridge can be inserted therein and to manually insert the film cartridge into the stretched device while the device is under tension. A portion of the film cartridge is typically inserted into the Marler device and then the Marler device is stretched to encompass the remainder of the film cartridge. This is a necessarily difficult task requiring a significant amount of manual dexterity and skill to accomplish.
The Strong-Grainger patents disclose a foam padding for a dental film cartridge. The padding of the Strong-Grainger device does not extend about the full perimeter of the film cartridge. Instead, it extends about approximately one-half the perimeter and thus does not provide complete protection. The padding of the Strong-Grainger device is more susceptible to loosening than the other prior art devices since it does not extend about the full perimeter of the film cartridge.
As such, although the prior art has recognized to a limited extent the problem of minimizing patient discomfort while obtaining the best quality dental radiographs, the proposed solutions have to date been ineffective in providing a satisfactory remedy.